In application Ser. No. 730,398, of which this application is a continuation-in-part, dimpling of a circular saw blade to produce discrete ridges raised from the plane of the blade, is described. The dimpling process produces a cold working effect, and the raised ridges provide protection against overheating of the blade and scorching of the workpiece when a planar side surface of the blade comes into contact with a wall defining the kerf being produced by the teeth of the blade. The present application is directed to an extension of that principle and technique to linear saw blades and other applications for which those principles and techniques have utility.
Producing small, discrete, surfaces projecting from a planar surface of a jigsaw, hacksaw, or band saw blade, for example, is counter-intuitive. Logically, clearance between the kerf produced by the teeth of the blade, and the body of the blade behind the teeth would be maximized. However, it is a matter of common knowledge that the bodies of jigsaw, hacksaw or band saw blades frequently come into contact with the walls defining the kerf of a workpiece. The provision of low-profile projections from such a blade reduces the surface of contact with the kerf wall.
In accordance with this invention, generally stated, low-profile, discrete protrusions are provided on the blade behind the teeth or cutting edge of a tool, in the form of ridges on the perimeters of indentations (concave dimples) or surfaces on the tops of domes (convex dimples). Preferably, the dimples are on both sides of the blade, although for some applications, protrusions on only one side may be desired. The dimples can be concave on one side and convex on the other, the same punching process forming both, or concave or convex dimples can be formed on both sides. Concave dimples with ridges at their perimeter can be formed in one or both sides, and convex dimples, without a corresponding concave dimple with a ridge, can be formed in one or both sides. The dimples can be of any perimetric configuration, i.e. circular, teardrop shaped, star shaped, polygonal, or even irregularly shaped, for example.
The dimples should be discrete, spaced from one another, and projecting on the order of 0.005 inches from a planar surface of the blade, although the dimensions of the dimples and their projection from the surface can vary with the application to which they are put.
The arrangement of the dimples can also be varied. For example, on a jigsaw blade, the narrowness of the blade dictates that the dimples be small and in either a linear or slightly staggered configuration. In a saber saw, band saw or hack saw, the width of the blade will permit a wider variety of pattern, or random distribution of dimples. In a hole saw, pruning saw, hand saw, or bow saw, for example, the patterns can be somewhat more open because of the greater width of the blade.